Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695-7624, USA.
Foodborne Pathog Dis. 2010 Sep;7(9):1125-8. doi: 10.1089/fpd.2009.0526.
Yersinia enterocolitica is a foodborne pathogen well known for its ability to grow at low temperatures. Recent studies with another psychrotrophic foodborne pathogen, Listeria monocytogenes, revealed that temperature of growth had pronounced impact on survival following repeated freezing and thawing (cryotolerance). Listerial cryotolerance was significantly more pronounced when bacteria were grown at 37 degrees C than following growth at either 4 degrees C or 25 degrees C. However, it is not known whether such impact of growth temperature is a general adaptation shared with other foodborne pathogens. In this study, we investigated the impact of growth temperature (4 degrees C, 25 degrees C, and 37 degrees C) on cryotolerance of Y. enterocolitica. In strong contrast to findings previously obtained with Listeria spp., cryotolerance of Y. enterocolitica was impaired following growth in liquid media at 37 degrees C, with cell concentration dropping to undetectable levels (<10(1) colony forming unit/mL) following as few as six freeze-thaw cycles. On the other hand, when the bacteria were grown at 4 degrees C, cryotolerance was significantly higher (p < 0.05), and substantial survival was maintained even after 18 cycles (2-5 log reduction, depending on strain). Enhanced cryotolerance was also observed with cultures grown at 25 degrees C. Bacteria grown at 37 degrees C on agar were significantly more cryotolerant than following growth at 37 degrees C in liquid media (p < 0.05). The data suggest species-specific impact of growth temperature and liquid versus agar medium on cryotolerance of cold-tolerant bacteria.
肠炎耶尔森菌是一种食源性病原体，其能够在低温下生长的能力是众所周知的。最近对另一种嗜冷食源性病原体李斯特菌的研究表明，生长温度对反复冷冻和解冻（耐寒性）后的存活有显著影响。当细菌在 37°C 下生长时，李斯特菌的耐寒性比在 4°C 或 25°C 下生长时更为明显。然而，目前尚不清楚这种生长温度的影响是否是与其他食源性病原体共同的普遍适应现象。在这项研究中，我们研究了生长温度（4°C、25°C 和 37°C）对肠炎耶尔森菌耐寒性的影响。与以前从李斯特菌属获得的发现形成强烈对比的是，在 37°C 下液体培养基中生长后，肠炎耶尔森菌的耐寒性受损，经过多达六次的冻融循环后，细胞浓度降至无法检测到的水平（<10(1)菌落形成单位/mL）。另一方面，当细菌在 4°C 下生长时，耐寒性显著提高（p<0.05），即使经过 18 次循环（取决于菌株，减少 2-5 个对数），也能保持显著的存活。在 25°C 下培养的细菌也观察到了增强的耐寒性。在琼脂上生长的细菌比在液体培养基中在 37°C 下生长的细菌具有更高的耐寒性（p<0.05）。数据表明，生长温度和液体与琼脂培养基对耐冷菌耐寒性的影响具有种特异性。
